Versão on line ISSN 1980-6477 - http://www.abms.org.br
OF ATRAZINE + S-METOLACHLOR TO DIFFERENT HYBRIDS
HUDSON KAGUEYAMA TAKANO1, AUGUSTO KALSING2, DAURI APARECIDO FADIN2,
ROGÉRIO DA SILVA RUBIN2, RODRIGO NEVES2 and LUIZ HENRIQUE MARQUES2
1Department of Bioagricultural Sciences and Pest Management, Colorado State University, 300 W Pitkin St, Fort Collins, Colorado, United States, 80526. E-mail: hudsontakano@gmail.com
2Corteva Agriscience™, Integrated Field Sciences, Mogi Mirim Research Center, Rodovia SP-147 Km 71.5,
Pederneiras – Mogi Mirim, São Paulo, Brazil, 13.800-970. augusto.kalsing@corteva.com; dauri.fadin@corteva.com; rsrubin@dow.com; rodrigo.neves@corteva.com; lhmarques@dow.com
Revista Brasileira de Milho e Sorgo, v.17, n.3, p. 460-473, 2018
ABSTRACT - Grain sorghum (Sorghum bicolor) is one cereal crop that faces huge problems with weed interference mostly because the lack of selective herbicides. This study aimed to assess the efficacy and safety of herbicide alternatives for weed control in grain sorghum as well as the selectivity of atrazine + s-metolachlor to different hybrids. Three field trials were designed as a randomized complete block with four replications. All experiments were conducted in Jardinópolis-SP and Mogi Mirim-SP during the 2015/16 growing season. Two trials included acetochlor, flumioxazin, fluroxypyr, mesotrione and s-metolachlor, applied in pre or post-emergence, in association or not with atrazine. A third trial was carried out with rates of the premix containing atrazine + s-metolachlor applied to the following hybrids: 1G100, 1G220, 1G230, 1G244, 1G282, 50A10, 50A40, 50A50 and 50A70. The pre-emergence herbicides that exhibited satisfactory efficacy of weed control and selectivity to sorghum crop were flumioxazin, atrazine + mesotrione and atrazine + s-metolachlor. For post-emergence, atrazine, atrazine + acetochlor, atrazine + s-metolachlor and atrazine + fluroxypyr were the best treatments for both efficacy and selectivity. The application of atrazine + s-metolachlor at the evaluated rates was considered selective to the nine hybrids assessed.
Keywords: acetochlor, fluroxypyr, mesotrione, herbicide tolerance, weed control.
MANEJO QUÍMICO DE PLANTAS DANINHAS EM SORGO GRANÍFERO E SELETIVIDADE DE ATRAZINE + S-METOLACHLOR PARA DIFERENTES HÍBRIDOS
RESUMO – O sorgo granífero (Sorghum bicolor) é um dos cereais de verão que mais enfrenta problemas com plantas daninhas em razão da interferência destas espécies e carência de herbicidas para controlá-las. O objetivo deste estudo foi avaliar a eficácia e segurança de herbicidas alternativos no controle de plantas daninhas em sorgo granífero, assim como a seletividade de atrazine + s-metolachlor para diferentes híbridos. Três experimentos foram realizados em campo com delineamento de blocos ao acaso e quatro repetições, sendo conduzidos em Jardinópolis-SP e/ou Mogi Mirim-SP, ao longo da safra 2015/16. Em dois experimentos, acetochlor, flumioxazin, fluroxypyr, mesotrione e s-metolachlor foram avaliados em pré e/ou pós-emergência da cultura, em associação ou não (isolados) com atrazine. O terceiro experimento foi realizado com doses crescentes de atrazine + s-metolachlor e os híbridos de sorgo granífero 1G100, 1G220, 1G230, 1G244, 1G282, 50A10, 50A40, 50A50 e 50A70. Os tratamentos com controle satisfatório de plantas daninhas e seletividade à cultura, em pré-emergência, foram flumioxazin, atrazine + mesotrione e atrazine + s-metolachlor. Em pós-emergência, eles foram atrazine, atrazine + acetochlor, atrazine + s-metolachlor e atrazine + fluroxipyr. A aplicação de atrazine + s-metolachlor nas doses testadas foi seletiva para os nove híbridos avaliados. Palavras-chave: acetochlor, fluroxypyr, mesotrione, tolerância a herbicidas, controle de plantas daninhas.
Grain sorghum (Sorghum bicolor) is one of the five most important cereal crops in Brazil and worldwide especially because its use as an energy source in human and animal nutrition (Mutisyat et al., 2009). World production of this cereal has been around 43 million tons, most in the United States, while Brazil contributes with about 4.5% of production (USDA, 2018). In Brazil, grain sorghum is usually grown with low levels of investment,
resulting in low average grain yields (2.8 tons ha-1)
(Acompanhamento da Safra Brasileira [de] Grãos, 2018). Yet, in the center-west region, this crop has gained special attention as a second crop, being considered an important alternative in crop rotation with soybean (Fonseca et al., 2008). This is due to the grain sorghum advantages as a wide sowing window and greater resistance to water stress, when compared to corn, which is commonly used as second crop (Borghi et al., 2016).
Among the summer cereals, grain sorghum is one that faces the greatest problems with weeds due to the negative interference of these species and lack of herbicides to control them. Estimates indicate that weeds can reduce up to 97% of the grain yield potential when there is no control (Rodrigues et al., 2010; Tamado et al., 2002). However, even using herbicides the outcome is not always as expected, particularly for grass species (Archangelo et al., 2002; Dan et al., 2010). In fact, only atrazine, simazine and 2,4-D are currently registered herbicides for grain sorghum cropping in Brazil, but the main target of these herbicides are broadleaved species (Brasil, 2003). Although atrazine applications may help in the control of some weeds, its efficacy is variable due to several factors, especially the weed species and its growth stage (Marchesan et al., 2013).
In recent years, several studies have investigated other herbicide alternatives for use in grain sorghum crops in order to provide new viable weed chemical management strategies. A well-studied and technically viable alternatives are the chloroacetamides, associated or not with atrazine, for post-emergence control (Archangelo et al., 2002; Takano et al., 2016). In a different way, other herbicides such as metsulfuron (Brown et al., 2004), fluroxypyr (Takano et al., 2016), flumioxazin (Galon et al., 2016), mesotrione (Abit et al., 2009) and tembotrione (Dan et al., 2010) have shown potential for use in grain sorghum crops, but they still lack more details regarding crop selectivity and technical positioning. So, additional information on herbicide rate, plant stage and interactions with climate and soil is required for a safe use of these herbicides in grain sorghum.
Other key aspect when one considers other chemical alternatives for the control of weeds in grain sorghum is the selectivity stability to their distinct hybrids. In corn, tolerance of commercial hybrids to sulfonylurea herbicides varies considerably, being high for some hybrids and low for others (Cavalieri et al., 2008). In addition, tolerance of maize hybrids may vary according to the environment, crop management system, herbicide rate and the plant stage during the herbicide application (Cavalieri et al., 2012; Guerra et al., 2010). In a study comparing five grain sorghum hybrids, the hybrid 50A50 was the least sensitive and recovered more rapidly on the evaluation of 18 herbicide treatments (Takano et al., 2016). Despite clearly showing different tolerances for different hybrid, this study was preliminary and did not investigate other variables relating to crop development and performance.
The objectives of the present study were to assess the efficacy and safety of herbicide alternatives
Revista Brasileira de Milho e Sorgo, v.17, n.3, p. 460-473, 2018 Versão on line ISSN 1980-6477 - http://www.abms.org.br
Figure 1 - Climate data collected during the conduction of the studies in
Jardinópolis-SP and Mogi Mirim-Jardinópolis-SP, 2016.
The experimental sites were sowed from March 15 to 27, 2016, using a seeder-fertilizer machine, simulating a conventional second-crop planting in Brazil. The hybrid 50A40 of grain sorghum was sowed with 18 seeds m-1 in rows, spaced 0.5 m,
aiming to reach a population of 320,000 plants ha-1. The agricultural practices used
were those recommended for the region, with investment for high grain yield (Borghi et al., 2016). The experimental sites were spray-irrigated to a water level of 10 mm when occurred drought for a period longer than seven days. The experimental units consisted of field plots measuring 3 x 4 m (12 m2) of useful land, containing six crop lines.
for weed control in grain sorghum, applied in pre- or post-emergence of the crop, as well as regarding the selectivity of atrazine + s-metolachlor to different hybrids of this cereal.
Material and Methods
Experimental areas and crop management Three trials were carried out during the 2015/2016 growth season in the municipalities of Mogi Mirim-SP (22°26’43”S; 47°04’02”W, 690 m altitude) and/or Jardinópolis-SP (20°54’39”S; 47°53’45”W, 560 m altitude), Brazil. The weather
conditions during the period are illustrated in Figure 1. Both areas had a history of summer crops, especially soybean and corn, and have used no-till system for at least 10 years. Prior to the installation of the trials, soil samples were collected for physicochemical analysis and recommended fertilization. The soils of the experimental sites were made of 15 and 57% of clay, 73 and 22% of sand, 12 and 21% of silt, with
5.5 and 5.4 pH (CaCl2) values, and 1.6 and 2.6% of
organic matter in Mogi Mirim-SP and Jardinópolis-SP, respectively. The spontaneous vegetation grown in the sites was eliminated fi ve days before implementation of the crop with application of 400 g
a.i. ha-1 of paraquat.
Figure 1 - Climate data collected during the conduction of the studies in Jardinópolis-SP and Mogi Mirim-SP, 2016.
The experimental sites were sowed from March 15 to 27, 2016, using a seeder-fertilizer machine, simulating a conventional second-crop planting in Brazil. The hybrid 50A40 of grain sorghum was
sowed with 18 seeds m-1 in rows, spaced 0.5 m, aiming
to reach a population of 320,000 plants ha-1. The
agricultural practices used were those recommended for the region, with investment for high grain yield (Borghi et al., 2016). The experimental sites were spray-irrigated to a water level of 10 mm when occurred drought for a period longer than seven days. The experimental units consisted of field plots
measuring 3 x 4 m (12 m2) of useful land, containing
six crop lines.
Efficacy and selectivity of pre-emergence herbicides (first trial)
The experimental design consisted of randomized blocks with four replications, and was replicated in two sites, Jardinópolis-SP and Mogi Mirim-SP. Treatments consisted of distinct herbicides applications during crop pre-emergence (“plant
and spray”), as follows (g ai ha-1): atrazine (2,000),
flumioxazin (60), atrazine + flumioxazin (2,000 + 60), mesotrione (100), atrazine + mesotrione (2,000 + 100), s-metolachlor (576, 770 and 1,150) and atrazine + s-metolachlor (2,000 + 576, 770 and 1,150). There was also an untreated check-plot (without application of herbicides) for comparison, where weeds were not controlled during the crop cycle. The same hybrids used for the post emergence experiment were employed in this experiment.
The herbicides were applied using a CO2
backpack sprayer equipped with 3-m long boom and six nozzles (AIXR 110.015) and calibrated for
100-L ha-1 of spray volume. The weeds assessed
were Amaranthus spp., Bidens pilosa and Portulaca oleraceae in Jardinópolis-SP and Amaranthus spp., Euphorbia heterophylla and Raphanus raphanistrum in Mogi Mirim-SP.
Efficacy and selectivity of post-emergence herbicides (second trial)
The experimental design, number of replications and locations were identical to the pre-emergence trial. Treatments consisted of distinct herbicides applied at the crop post-emergence (3-4
leaves stage) as follows (g a.i. ha-1): atrazine (2,000),
acetochlor (1,150 and 2,300), atrazine + acetochlor (2,000 + 1,150 and 2,300), fluroxypyr (100 and 120), atrazine + fluroxypyr (2,000 + 100 and 120), mesotrione (50 and 100), atrazine + mesotrione (2,000 + 50 and 100), s-metolachlor (576 and 770) and atrazine + s-metolachlor (2,000 + 576 and 770). In this experiment, it was also added an untreated check-plot without herbicides application. The herbicides were applied as described in the previous experiment.
On the day of the herbicides application, the following weed species were visually evaluated: Amaranthus viridis (13 plants m-2) and Raphanus raphanistrum (32 plants m-2), staged at 2 to 4 leaves, in Mogi Mirim-SP; Amaranthus viridis (33 plants
m-2) and Portulaca oleracea (5 plants m-2), staged at
2 to 4 leaves, in Jardinópolis-SP.
Selectivity of atrazine + S-metolachlor to sorghum hybrids (third trial)
The experimental design and number of replicates were identical to the previous experiments; however, in this case, the experiment was conducted only in Jardinópolis-SP. The experiments were
Revista Brasileira de Milho e Sorgo, v.17, n.3, p. 460-473, 2018 Versão on line ISSN 1980-6477 - http://www.abms.org.br
arranged in factorial design with subdivided plots (A = 3 x B = 9), with Factor A being allocated to the plots, and Factor B to the sub-plots. Factor A consisted of three rates of the pre-mixture atrazine + s-metolachlor applied in the crop post-emergence (3 to 4 leaves) (g
a.i. ha-1): 0, 1,480 + 1,160 and 2,960 + 2,320. In this
case, besides serving as a comparison pattern for the herbicides treatments, the untreated check-plot was also one of the levels of treatments tested for Factor A. Factor B consisted of nine sorghum hybrids with different levels of sensitivity to herbicides (Takano et al., 2016): 1G100, 1G220, 1G230, 1G244, 1G282, 50A10, 50A40, 50A50 and 50A70. Application of the treatments was carried out as described for the other
experiments, and Amaranthus spp. (33 plants m-2)
was the only weed evaluated. Evaluations and statistical analysis
The efficacy of weed control was assessed 21 and 42 days after application (daa) and crop injury 14, 21 and 42 daa, using a visual scale ranging from 0 to 100%. In addition, the number of days between
the plants emergence and 50% flowering (F50), the
crop population and height during full blossom were also evaluated. Finally, crop grain yield was assessed by harvesting the four central lines of the plot, and normalizing the values found to the standard grain moisture of 13%. The data were subjected to analysis of variance by the F-test for significant effects (p<0.05) and Tukey’s pairwise comparison test for mean separation of the tested treatments. When the effect of sites and its interactions was not significant, the locations were considered as a random variable because there was homogeneity of error variances (Zimmermann, 2004).
Results and Discussion
A joint analysis of the data of Jardinópolis-SP and Mogi Mirim-Jardinópolis-SP was made for the majority of the variables, except for efficacy of control, where significant differences were found at the sites (p<0.05). So, the treatments values for this variable are shown in separate by location, while for the other variables are considered the means derived from the means of both places.
Efficacy and selectivity of pre-emergence herbicides (first trial)
In general, the efficacy of weed control in the treatments had mean values of at least 90%, especially when atrazine was associated with other residual herbicides (Table 1). In fact, these associations provided a high control of all species examined, except Portulaca oleraceae, which indicated 83-86% of control with atrazine and mesotrione. However, when applied alone the effect of the herbicides was not always satisfactory, such as of atrazine applied in both sites, and s-metolachlor in the experimental site in Mogi Mirim-SP. Control was higher than 90% only with flumioxazin applied alone, for most of the weeds in both assessments.
Regarding crop injury, a great variability of response was found in the treatments tested, atrazine being the only herbicide that caused less than 5% of injury in the three assessments (Table 2). Mesotrione, flumioxazin and their mixtures with atrazine caused maximum injury levels of 20%, which declined over time and remained below 10% at 42 daa. In the case of s-metolachlor, an effect of the dose-response was observed for the magnitude of this variable since the grain sorghum injury increased as the rate of the
T ab le 1. E ff ica cy o f w ee d c ontrol afte r appli ca tion of pr e-em er ge nc e he rbicide s on gr ain sor ghu m ( 50A40 ). J ardinóp oli s-SP a nd Mog i Mi rim -SP, 2 016. Tr ea tm en t Do se (g a i ha -1 ) Ja rdi nópol is -SP Mo gi M iri m -SP A M ASS 1/ B IDP I POR OL A M ASS EP HHL RA PRA 21 da a 2/ 42 da a 21 da a 42 da a 21 da a 42 da a 21 da a 42 da a 21 da a 42 da a 21 da a 42 da a Un trea ted 0 0 0.0 0 0 0 0 0 0 0 0 0 0 Me so trio ne 100 97 A 3/ 96 a 98 a 97 a 82 c 68 b 95 97 a 94 a 92 96 a 96 a S-m eto lac hlo r 576 93 a 86 a 93 a 90 a 93 ab 92 a 94 82 b 67 b 90 61 b 52 b S-m eto lac hlo r 770 94 a 90 a 95 a 91 a 97 a 95 a 94 85 b 79 ab 92 74 ab 68 ab S-m eto lac hlo r 1150 96 a 93 a 97 a 96 a 98 a 97 a 95 85 b 93 a 91 88 a 84 a Flu m io xaz in 60 100 a 100 a 100 a 100 a 100 a 100 b 98 98 a 97 a 97 96 a 88 a A traz in e 2000 70 b 64 b 81 b 74 b 84 c 80 ab 91 91 ab 95 a 91 87 a 88 a A traz in e + m es otr io ne (2 ,00 0 + 1 00) 98 a 96 a 99 a 98 a 86 bc 83 ab 99 100 a 99 a 100 98 a 98 a A traz in e + s -m eto lach lo r (2 ,00 0 + 5 76) 96 a 96 a 95 a 96 a 98 a 99 a 99 98 a 96 a 96 96 a 94 a A traz in e + s -m eto lach lo r (2 ,00 0 + 7 70) 97 a 95 a 98 a 97 a 97 a 97 a 98 98 a 99 a 98 91 a 88 a A traz in e + s -m eto lac hlo r (2 ,00 0 + 1 150 ) 99 a 96 a 98 a 96 a 99 a 97 a 98 99 a 98 a 98 94 a 89 a A traz in e + flu m io xaz in (2 ,00 0 + 6 0) 100 a 100 a 100 a 100 a 100 a 100 A 98 98 a 99 a 99 93 a 94 a F 24. 6 7.3 2.5 2.1 6.4 5.6 1 .3 ns 1.6 14. 0 1 .2 ns 13. 2 14. 4 C V ( %) 3.6 8.3 10. 7 12. 6 5.7 10. 6 21. 0 11. 4 47. 9 46. 7 58. 8 52. 6 DM S 8.4 18. 8 20. 9 21. 8 13. 3 22. 8 41. 2 15. 3 21. 8 27. 9 22. 5 21. 2 1/ A M ASS: A m ar ant hus sp p. , B IDP I: Bi den s p ilo sa , P OR OL : P or tu la ca o lera ce ae , R AP R A: R aphanus rap hani str um an d E PHH L: E uphor bi a he te rophy lla . 2/ daa : d ay s af ter ap plicatio n 3/ M ea ns f ollo w ed b y the sa m e letter d o n ot dif fer f ro m ea ch o th er b y t he Tu ke y’ s test ( p<0 .0 5) . Table 1. Efficacy of weed control after application of pre-emer gence herbicides on grain sor ghum (50A40). Jardinópolis-SP and Mogi Mirim-SP , 2016. 1/AMASS: Amaranthus spp., BIDPI: Bidens pilosa , POROL: Portulaca oleraceae , RAPRA: Raphanus raphanistrum and EPHHL: Euphorbia heter ophylla .
2/daa: days after application 3/ Means followed by the same letter do not dif
fer from each other by the
Tukey’
Revista Brasileira de Milho e Sorgo, v.17, n.3, p. 460-473, 2018 Versão on line ISSN 1980-6477 - http://www.abms.org.br
herbicide increased. Less than 20% of injury was
observed in the plots treated with 576 g ha-1, while in
the plots with 770 and 1,150 g ha-1 injury levels were
higher than 50%.
The population of grain sorghum was reduced only in the plots treated with s-metolachlor at 770 and
1,150 g ha-1, which were statistically different from
the untreated check-plot (Table 2). The crop height was only lower with application of s-metolachlor at
1,150 g ha-1, associated or not with atrazine, when
compared to the control. The number of days between the plants emergence and 50% of flowered sorghum
plants (F50) was smaller for the treatment with
atrazine only and for the untreated check-plot, when
compared to the s-metolachlor (1,150 g ha-1) alone or
mixed with atrazine. The crop grain yield was only reduced with application of s-metolachlor (1,150 g
ha-1), associated or not with atrazine, while the yields
in the other treatments were not reduced.
Efficacy and selectivity of post-emergence herbicides (second trial)
In most cases, the efficacy of control values was higher than 95% in the plots treated with atrazine and its associations with other herbicides, in both assessments (Table 3). However, when applied alone (not associated with other herbicides), the effect was unsatisfactory (<90%), although no significant statistical difference was always found. In fact, acetochlor, s-metolachlor and fluroxypyr did not achieve a satisfactory efficacy for Amaranthus spp., P. oleracea and R. raphanistrum, regardless of herbicide rate and experimental site. For mesotrione, the effect was satisfactory for Amaranthus spp., in both sites, and for R. raphanistrum in Jardinópolis-SP, but not for P. oleracea in Jardinópolis-SP.
Concerning crop injury, most of the treatments indicated high selectivity to the grain sorghum hybrid 50A40, with mean values lower than 5%, in the three assessment dates (Table 4). Acetochlor associated with atrazine with the highest rate tested caused injuries ranging from 6 to 10%, but did not differ statistically from the other treatments with the herbicides tested. Mesotrione and its associations with atrazine caused the greatest injury levels to the
crop, either at 50 g ha-1 or 100 g ha-1, in the three dates
of visual assessment of the symptoms. While with the exclusive application of mesotrione the injury levels ranged from 12 to 27%, the magnitude of the effect of its association with atrazine was greater, with values ranging from 40 to 55%.
The crop population and height did not vary as a result of the treatments studied (data not presented).
The F50 value was higher for the association of the
atrazine + mesotrione (2,000 + 100 g ha-1) herbicides
than for the untreated check-plot, as described in Table 4. Crop grain yield was lower only for the treatment
with atrazine + mesotrione (2,000 + 100 g ha-1), when
compared with the untreated check-plot. Therefore, in the plots treated with atrazine + mesotrione (2000
+ 50 g ha-1), as well as with the other herbicides
tested, there was not a decrease in yields that might be caused by the treatments.
Selectivity of atrazine + s-metolachor to sorghum hybrids (third trial)
The efficacy of control of Amaranthus spp. at 28 daa varied only as a function of the rate of the atrazine + s-metolachor, applied in a pre-formulated mixture, as shown in Figure 2. It can be seen that the efficacy of control provided by both dosages of herbicide was over 98%, and the control obtained
Table 2. V isual injury , crop height, crop stand, flowering time of 50% of the plants (F 50
) and crop grain yield after
application
of
pre-emer
gence herbicides on grain sor
ghum (50A40). Jardinópolis-SP
and Mogi Mirim-SP
, 2016.
1/daa: days after application; 2/Mean values of both sites by the joint analysis. Means followed by the same letter do not dif
fer from each other by the
Tukey’ s test (p<0.05). T ab le 2. Visua l in jur y, crop he ig ht, crop stand , flow erin g ti me of 50% of the plants (F50 ) a nd crop gra in yield a fte r appl ica tion of pr e-emer ge nc e he rbic ides on gr ain sor ghum (50A40 ). J ardinóp oli s-SP a nd Mogi Mi rim -S P, 2016. Tr ea tm en t Do se (g a i ha -1 ) Vis ua l in ju ry (%) Heig ht (c m) Stan d (p l. m -1 ) F50 (d ias) Yield (kg ha -1 ) 2/ 14 da a 1/ 21 da a 42 da a Un trea ted 0 0 0 0 132 a 18 a 69 bc 5, 529 ab c Me so trio ne 100 8 d 2/ 7 e 3 cd 131 a 16 ab 70 ab c 6, 505 a S-m eto lac hlo r 576 16 bcd 14 de 9 b cd 128 ab 16 ab 70 ab c 5, 850 ab S-m eto lac hlo r 770 33 bc 29 cd 13 bc 128 ab 14 b 70 ab c 5, 221 ab c S-m eto lac hlo r 1150 59 a 55 a 43 a 125 b 14 b 72 ab 4, 199 c Flu m io xaz in 60 20 bcd 15 de 9 b cd 130 ab 15 ab 70 ab c 6, 044 ab A traz in e 2000 4 d 4 e 1 d 131 a 17 ab 68 c 6, 367 ab A traz in e + m es otr io ne (200 0 + 1 00) 15 cd 15 de 4 cd 130 ab 16 ab 70 ab c 6, 061 ab A traz in e + s -m eto lach lo r (200 0 + 5 76) 17 bcd 14 de 6 cd 130 ab 15 ab 70 ab c 5, 820 ab A traz in e + s -m eto lach lo r (200 0 + 7 70) 38 ab 36 bc 20 b 127 ab 15 ab 71 ab c 5, 717 ab A traz in e + s -m eto lach lo r (200 0 + 1 150) 59 a 54 ab 43 a 125 b 15 ab 73 a 5, 016 bc A traz in e + flu m io xaz in (200 0 + 6 0) 17 bcd 17 cd e 7.1 cd 130 ab 15 ab 70 ab c 5, 440 ab c F 15 .6 18. 9 35. 2 4.5 2.5 3.6 14. 7 C V ( %) 52 .1 48. 5 49. 6 1.7 9.6 1.8 14. 5 DM S 22 .7 19. 3 11. 7 3.2 2.2 3.1 1 ,38 7. 2 1/ daa : d ay s af ter ap plicatio n; 2/ Me an v alu es o f b oth s ite s b y th e jo in t an al ys is . M ea ns fo llo w ed b y the s am e letter d o n ot dif fer f ro m ea ch o th er b y th e Tu ke y’ s test ( p<0 .0 5) .
Revista Brasileira de Milho e Sorgo, v.17, n.3, p. 460-473, 2018 Versão on line ISSN 1980-6477 - http://www.abms.org.br
Table 3. Efficacy of weed control after application of post-emer gence herbicides on grain sor ghum (50A40). Jardinópolis-SP and Mogi Mirim-SP , 2016. 1/AMASS: Amaranthus spp.. POROL: Portulaca oleraceae , RAPHA: Raphanus raphanistrum .
2/daa: days after application. 3/ Means followed by the same letter do not dif
fer from each other by the
Tukey’ s test (p<0.05) T ab le 3. E ff ica cy o f w ee d c ontrol afte r appli ca tion of post -e mer ge nc e he rbic ides on gr ai n sor ghu m ( 50A40 ). J ardinópoli s-SP a nd Mog i Mi rim -SP, 2016. Tr ea tm en t Do se (g a i ha -1 ) Ja rdi nópol is -SP Mo gi M iri m -SP A M ASS 1/ POR OL A M ASS RA PRA 7 da a 2/ 28 da a 7 da a 28 da a 7 da a 28 da a 7 da a 28 da a Un trea ted 0 0 0 0 0 0 0 0 0 A ce to ch lo r 1150 76 abc 3/ 71 ab 73 bcd 67 b 26 e 66 d 24 fg 65 b A ce to ch lo r 2300 73 ab c 77 ab 82 ab c 80 ab 26 e 60 d 22 g 59 b Me so trio ne 50 60 cd 97 a 43 d 61 b 85 b 97 bc 82 b 95 a Me so trio ne 100 86 ab 98 a 73 bcd 69 ab 85 b 99 ab c 84 b 96 a S-m eto lac hlo r 576 50 d 48 b 50 cd 54 b 28 e 35 e 25 fg 31 c S-m eto lac hlo r 770 58 cd 66 ab 54 cd 63 b 35 de 59 d 34 e 59 b Flu ro xy py r 100 65 bcd 77 ab 68 cd 81 ab 43 c 65 d 42 d 64 b Flu ro xy py r 120 73 ab c 75 ab 85 ab c 82 ab 32 de 66 d 31 ef 66 b A traz in e 2000 95 a 96 a 97 ab 97 a 98 a 97 bc 96 a 95 a A traz in e + ac eto ch lo r (200 0+ 11 50) 99 a 99 a 99 a 100 a 94 a 99 ab 93 a 98 a A traz in e + ac eto ch lo r (200 0+ 23 00) 86 ab 98 a 96 ab 99 a 97 a 99 ab c 96 a 98 a A traz in e + m es otr io ne (200 0+ 50) 100 a 100 a 100 a 100 a 97 a 100 a 94 a 98 a A traz in e + m es otr io ne (200 0+ 10 0) 100 a 100 a 100 a 100 a 98 a 100 a 98 a 98 a A traz in e + s -m eto lach lo r (200 0+ 57 6) 100 a 100 a 100 a 100 a 97 a 100 a 97 a 99 a A traz in e + s -m eto lach lo r (200 0+ 77 0) 100 a 100 a 100 a 100 a 99 a 100 a 97 a 98 a A traz in e + flu ro xy py r (200 0+ 10 0) 95 a 98 a 98 ab 98 a 97 a 98 ab c 96 a 97 a A traz in e + flu ro xy py r (200 0+ 12 0) 100 a 100 a 100 a 100 a 98 a 100 a 96 a 98 a F 17. 1 11. 7 17. 6 14. 5 247. 2 169 .6 215. 9 18 6. 6 C V ( %) 14. 4 16. 3 15. 4 15. 2 5 .8 4.9 6.3 4.7 DM S 16. 7 19. 9 15. 3 17. 9 5 .9 2. 1 6.4 5.5
Table 4. V isual injury , flowering time of 50% of the plants (F 50
) and crop grain yield after application
of post-emer
gence herbicides on
grain sor
ghum (50A40). Jardinópolis-SP
and Mogi Mirim-SP
. 2016.
1/daa: days after application; 2/Mean values of both sites by the joint analysis. Means followed by the same letter do not dif
fer from each other by the
Tukey’ s test (p<0.05). T ab le 4. Visua l inj ur y, flow ering time of 50% of the plants (F50 ) a nd c ro p gr ain yi eld afte r a ppli ca tion of post -e mer ge nc e he rbic ides on gr ain sor ghum (50A40 ). Ja rdinóp oli s-SP a nd Mogi Mi rim -S P. 2016. Tr ea tm en t Do se (g ai ha -1 ) Vis ua l in ju ry (%) F50 (d ays ) Gr ain y ie ld (kg ha -1 ) 2/ 7 da a 1/ 14 da a 28 da a Un trea ted 0 0 0 0 68 b 4, 907 ab A ce to ch lo r 1150 2 c 2/ 2 c 0 b 68 b 6, 057 ab A ce to ch lo r 2300 3 b c 2 c 3 b 68 b 6, 384 ab Me so trio ne 50 12 bc 16 bc 17 ab 69 ab 6, 311 ab Me so trio ne 100 25 b 18 bc 26 ab 69 ab 5, 532 ab S-m eto la chl or 576 1 c 1 c 2 b 68 b 5, 747 ab S-m eto lac hlo r 770 1 c 1 c 2 b 69 ab 5, 712 ab Flu ro xy py r 100 1 c 0 c 1 b 69 ab 5, 646 ab Flu ro xy py r 120 1 c 1 c 1 b 70 ab 5, 425 ab A traz in e 2000 1 c 2 c 1 b 72 a 6, 489 a A traz in e + ac eto ch lo r (2. 00 0 + 1 .15 0) 4 b c 4 c 3 b 68 b 6, 585 a A traz in e + ac eto ch lo r (2. 00 0 + 2 .30 0) 6 b c 7 c 9 b 70 ab 6, 163 ab A traz in e + m es otr io ne (2. 00 0 + 5 0) 51 a 43 ab 40 a 69 ab 4, 537 ab A traz in e + m es otr io ne (2. 00 0 + 1 00) 49 a 55 a 41 a 72 a 4, 320 b A traz in e + s -m eto lach lo r (2. 00 0 + 5 76) 2 c 1 c 0 b 69 ab 5, 988 ab A traz in e + s -m eto lach lo r (2. 00 0 + 7 70) 2 c 1 c 1 b 69 ab 6, 490 a A traz in e + flu ro xy py r (2. 00 0 + 1 00) 0 c 1 c 0 b 68 b 6, 626 a A traz in e + flu ro xy py r (2. 00 0 + 1 20) 2 c 1 c 4 b 69 ab 6, 479 a F 14. 0 5.8 5.9 2.9 12 .6 CV (% ) 126. 1 195. 8 172. 8 1.4 18 .9 DM S 22. 4 33. 9 28. 9 2.5 2. 076. 9 1/ daa : d ay s af ter ap plicatio n; 2/ Me an v alu es o f b oth site s b y th e jo in t a nal ys is . M ea ns fo llo w ed b y the sa m e letter d o n ot dif fer fr om ea ch o th er b y th e Tu ke y’ s te st (p <0 .0 5) .
Revista Brasileira de Milho e Sorgo, v.17, n.3, p. 460-473, 2018 Versão on line ISSN 1980-6477 - http://www.abms.org.br
with the greater rate was significantly higher than that of the lower rate.
Regarding crop injury, there was a variation resulting from the interaction between the factors related to the rate of atrazine + s-metolachor and sorghum hybrids (Table 5). Higher levels of injuries were observed with increased herbicide rate in all hybrids except for 50A10 and 50A40, whose tolerance level was not affected by the treatment. The hybrid 1G220 exhibited higher levels of visual injury, with values in the range of 8 to 28%, and was statistically different from the other hybrids tested in this work. The other hybrids tested always indicated injury levels lower than 11%, especially 1G233, 50A10 and 50A40, whose injury level never exceeded the mean value of 5%.
Grain yields also varied as a function of the interaction between the factors relating to rate of atrazine + s-metolachor herbicide and grain sorghum hybrids, as shown in Table 5. In general, the increased herbicide rate caused an increase in this variable magnitude, since the highest values were found for
rate of 2960 + 2320 g ha-1. However, the rate effect
could only be observed in four of the nine possible comparisons, since there was no statistical difference between the herbicide rates in most of the cases. Despite the potential yield of the different grain sorghum hybrids in Jardinópolis-SP, hybrid 1G220 and 1G282 varieties had the highest yields compared to the other hybrids.
Weed interference constrains sorghum grain yields in Brazil and is exacerbated by lack of effective
Table 5. Visual injury
1/and crop grain yield as a result of different hybrids and
[atrazine + S-metolachlor] rates on grain sorghum crop. Jardinópolis-SP, 2016.
Hybrid*
Visual injury (%) Grain yield (kg ha-1)
Atrazine + S-metolachlor [g i.a. ha-1]
0 [1480+1160] [2960+2320] 0 [1480+1160] [2960+2320] 1G100 02/ C 3 bc B 6 c A 3,992 ab AB 3,191 ab B 5,271 abc A 1G220 0 C 8 a B 28 a A 3,760 ab A 3,050 c A 4,476 c A 1G233 0 B 1 bc B 4 cd A 5,819 a AB 4,652 ab B 7,317 a A 1G244 0 B 0 c B 5 cd A 4,240 ab A 3,656 ab A 4,907 bc A 1G282 0 B 2 bc B 11 b A 3,370 c B 4,573 ab AB 4,608 c A 50A10 0 A 1 bc A 1 d A 3,941 ab A 4,754 ab A 5,960 abc A 50A40 0 A 1 bc A 4 cd A 5,528 a AB 5,060 ab B 6,860 ab A 50A50 0 C 3 bc B 7 bc A 5,398 ab A 5,072 ab A 5,119 bc A 50A70 0 B 1 bc B 7 bc A 4,842 ab A 5,245 a A 6,251 abc A DMS row 2.6 1587.7 DMS colum 4.2 2129.2 CV 30.3 16.6 F 25.9 1.6
1/ Means followed by the same lowercase letter in the column and uppercase in the row not differ from
each other by the Tukey’s test (p<0.05). 2/ Evaluated at 28 days after application.
Table 5. Visual injury1/ and crop grain yield as a result of different hybrids and [atrazine + S-metolachlor] rates on grain sorghum crop. Jardinópolis-SP, 2016.
herbicide options. Furthermore, even with the use of registered herbicides, the outcome is not always as expected, especially for grass weeds (Archangelo et al., 2002; Dan et al., 2010). Prospection of new herbicide alternatives is necessary to overcome this problem, either with products already available in the market or those under development. The present work contributes with alternatives for use in pre-emergence (Tables 1 and 2) and post-emergence (Tables 3 and 4) crops, both with good results in weed control and crop selectivity. In addition, the study shows that the pre-mix atrazine + s-metolachlor has a high level of selectivity to the most hybrid varieties of sorghum (Table 5, Figure 2).
Flumioxazin and mesotrione, applied alone or in combination with atrazine, achieved satisfactory levels of efficacy and selectivity (Tables 1 and 2).
In other studies, the use of flumioxazin (50 g ha-1)
and mesotrione (105 g ha-1) in this condition was
also promising (Abit et al., 2009; Galon et al., 2016).
Added to these herbicides, s-metolachlor (576 g ha
-1) was also another selective alternative to the crop,
although its efficacy has not always been satisfactory, being required its association with atrazine (Tables
1 and 2). However, with rates of 770 g ha-1 and
1,150 g ha-1, the use of this herbicide should not be
recommended because of the high levels of injury caused to the crop, especially in sandy soils. In contrast, atrazine + s-metolachlor with rates of 1,120
+ 1,400 g ha-1 (Geier et al., 2009) or 1,000 + 800 g ha-1
(Takano et al., 2016) exhibited selectivity to grain in pre-emergence condition.
In the case of application of post-emergence herbicides, diverse combinations with atrazine and acetochlor, s-metolachlor and fluroxypyr indicated satisfactory efficacy of control and selectivity to the crop (Tables 3 and 4). These combinations
also exhibited promising results in preliminary studies (Takano et al., 2016), and their use prevents the selection of triazine-resistant weed biotypes (Geier et al., 2009). In addition to these herbicides,
mesotrione (50 g ha-1) was also an interesting
option, even causing low-to-moderate injuries, which however did not affect the crop development and crop grain yield. These results corroborate those found by Hugie et al. (2008) and Abit et al. (2009), where mesotrione was a major option for the control of Amaranthus spp. Furthermore, this herbicide exhibited a high level of control of grass weeds such as Brachiaria spp., Digitaria spp., among others, and can be used with this purpose in grain sorghum crops.
The results obtained in the study with different grain sorghum hybrids showed that there is a special tolerance to atrazine + s-metolachlor, and that selectivity is associated with the herbicide rate (Table 5). These differences were also found in a preliminary study with grain sorghum (Takano et al., 2016) and have been widely known and studied for different maize hybrid (Cavalieri et al., 2008, 2012). Therefore, the choice of the herbicide and rate to be applied, the hybrid variety to be planted and the crop management system should be taken into account in the strategy of weed control. For the particular case of the pre-formulated mixture of atrazine + s-metolachlor, with dose of 1,480 + 1,160
g a.i ha-1, there is high selectivity stability among
the commercial hybrids of this crop. This ensures the safe use of this new option for weed chemical control, and the effect of these herbicides will be a high level of control of a wide range of species (Table 4, Figure 2).
Although it is the most used herbicide for weed control in grain sorghum crops in Brazil, atrazine
Revista Brasileira de Milho e Sorgo, v.17, n.3, p. 460-473, 2018 Versão on line ISSN 1980-6477 - http://www.abms.org.br
applied alone did not indicate good control of part of the weeds under evaluation in this study (Table 2). This shows the importance of its association with other residual herbicides in pre-and post-emergence conditions, which benefits the effect obtained with the use of chemical control. The herbicides combinations that exhibited satisfactory weed control and selectivity to grain sorghum in the crop pre-emergence were: atrazine + flumioxazin
(2,000 + 60 g ha-1), atrazine + mesotrione (2,000
+ 100 g ha-1) and atrazine + S-metolachlor (2,000
+ 576 g ha-1). In the crop post-emergence, the
best herbicide combinations were: atrazine +
acetochlor (2,000 + 1150 and 2300 g ha-1), atrazine
+ s-metolachlor (2,000 + 576 and 770 g ha-1) and
atrazine + fluroxipyr (2,000 + 100 and 120 g ha
-1). These management strategies would provide
benefits such as the rotation of herbicides action mechanisms, an increased range of weeds control, especially grasses, in the case of acetochlor, s-metolachlor and mesotrione.
Conclusion
The pre emergence herbicide alternatives that best optimized weed control and crop selectivity
were flumioxazin (60 g ha-1), atrazine + flumioxazin
(2,000 + 60 g ha-1), atrazine + mesotrione (2,000+100
g ha-1) and atrazine + S-metolachlor (2,000 +
576 g ha-1). The best post emergence herbicide
alternatives were atrazine (2,000 g ha-1), atrazine +
acetochlor (2,000 + 1,150 and 2,300 g ha-1), atrazine
+ s-metolachlor (2,000 + 576 and 770 g ha-1) and
atrazine + fluroxypyr (2,000 + 100 and 120 g ha-1).
The application of atrazine + s-metolachlor at the evaluated rates was selective to the nine hybrids assessed.
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![Table 5. Visual injury 1/ and crop grain yield as a result of different hybrids and [atrazine + S-metolachlor] rates on grain sorghum crop](https://thumb-eu.123doks.com/thumbv2/123dok_br/15567959.1047684/11.892.86.811.586.997/table-visual-injury-different-hybrids-atrazine-metolachlor-sorghum.webp)
